Osteoarthritis (OA) onset and progression is thought to be related to altered mechanical loading during daily activities. A fibrocartilagenous structure within the knee called the meniscus serves to distribute load across the joint to protect the underlying articular cartilage and bone and is known to move as the knee flexes and extends. Abnormal meniscal movement during tasks such as walking and other activities of daily living may play an important role in the onset and progression of knee OA. The current proposal uses advanced quantitative magnetic resonance imaging (MRI) techniques to evaluate meniscal motion, cartilage compositional changes, joint contact mechanics, and radiological grading of disease severity. One hundred subjects with and without knee OA will undergo kinematic-MRI and relaxation time mapping for cartilage and meniscus composition. Both cross-sectional (OA vs. controls) and longitudinal (3 times over two years) aims are proposed. Characterizing meniscal kinematics in the OA knee and the relationship to joint health will give a novel and powerful understanding of the mechanisms behind incidence and progression of knee OA. We hypothesized that greater meniscal motion will be associated with worse outcomes over time. This knowledge may be directly translated to the clinical setting since altered meniscal movement and morphology may be treated through surgical intervention, and targeting treatment specifically to those individuals that have the greatest risk for cartilage degeneration. Specific Aim 1: Evaluate meniscus movement and cartilage composition in health controls and subjects with knee OA. Specific Aim 2: To determine the longitudinal change over two years in meniscus kinematics in controls and subjects with knee OA; and to determine the predictive capability of baseline meniscal kinematics at determining disease progression. Specific Aim 3: To characterize meniscus kinematics in high knee flexion in a sub-group of subjects, to determine if 60 or 90 degree knee angles are more predictive of articular cartilage composition. The three proposed aims serve to give the applicant training in MR image acquisition, post-processing, and improved clinical research perspectives on longitudinal analyses and study design. The research-training program includes course work in designing and implementing clinical research, a rich research environment, and structured mentoring for the applicant.